Method and apparatus for controlling fecal odors

ABSTRACT

Methods and apparatus for controlling fecal odors in an enclosed space, such as a pit latrine, include providing an oxidizer, such as a catalytic heater and an optional mechanical ventilation unit, such as an inline fan, both flow connected to a vault (pit) of the latrine. The heater is also connected to a source of fuel, for example, propane. Fresh air is drawn through vents in the latrine housing and thereafter through toilets in the latrine and through the vault, providing oxygen for the reaction. The fan and/or oxidation process draws both fresh air and accompanying odorous compounds directly from the latrine and into the oxidizer wherein the odorous components are substantially destroyed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional application No.60/842,828 filed Sep. 7, 2006, the disclosure of which is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to improved apparatus and methods forcontrolling fecal and other human or animal body odors from asubstantially enclosed space and in particular for withdrawing andincinerating odorous gasses from pit latrines.

Pit latrines suffer from bad odor due to the confined nature of the pitand the waste deposited into the pit. The addition of heat during thebusy summer months amplifies the odor problem. Often, pit latrines arelocated in remote areas. Thus, it may not be possible to equip a pitlatrine with sufficient ventilation, for example, elevated stacks, toreduce latrine odor. Even in situations where electricity is available,mechanical ventilation, such as an exhaust fan, may remove some of thelatrine odor from an enclosed area, but then merely move the odor toanother area that can still create an undesirable odor in a publicplace, such as a park located near the pit latrine. Therefore, it wouldbe desirable to have a method and relatively simple apparatus fordeodorizing a pit latrine that does not merely move the offending odorsfrom one location to another.

It is known in the art to remove noxious gas, such as sewer gas, byflaring the gas. A variety of patent publications disclose burners forigniting noxious gasses from, for example, sewers, mines and landfills.However, the use of open flames are not desirable in remote settingsand/or settings visited by the general population, such as public parks.

SUMMARY OF THE INVENTION

Methods and apparatus according to the invention for controlling fumesfrom an enclosed space, such as a pit latrine, having a waste reservoiror vault connected to one or more toilets includes directly connectingthe vault to an incinerator or oxidizer. Preferably, the incinerator isflame-less. Most preferably the incinerator is a catalytic heater thatutilizes an easily obtained fuel, such as propane, for the oxidationprocess. As an oxygen source for the process, fresh air (from existingvents in the latrine housing) and noxious latrine fumes are drawn intothe incinerator through the toilets and then the latrine vault by theoxidation process being performed in the incinerator. A ventilation unitsuch as an in-line fan can be utilized with the process to increase thespeed and/or volume of air flow and accompanying odors drawn from thevault into the incinerator. The latrine is thus ventilated with onlyfresh air, with positive air flow being pulled through the toilets.Furthermore, hot deodorized gas that leaves the incinerator may be useddirectly or indirectly to warm the pit latrine housing in cold weather.

OBJECTS AND ADVANTAGES OF THE INVENTION

Therefore, objects of the present invention include: providing methodsand apparatus for deodorizing the user space of pit latrines and otherenclosed spaces located adjacent to fecal matter; providing such methodsand apparatus that safely remove noxious odors from a public user spacethrough the pit latrine vault; providing such methods and apparatus thatoxidize pit latrine gas without using a flame; providing such methodsand apparatus that utilize commercially available flame-less heaters;providing such methods and apparatus that further utilize mechanicalventilation; providing such methods and apparatus that are inexpensiveto produce and especially well adapted for the intended usage thereof.

Other objects and advantages of this invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general schematic representation of a process according tothe invention.

FIG. 2 is a more detailed schematic view of a process and apparatusaccording to the invention.

FIG. 3 is a partially schematic side elevational view of an apparatusand method of the invention that includes a vault pump-out connectionand grade mounted unit.

FIG. 4 is a partially schematic top plan view of the apparatus andmethod of FIG. 3.

FIG. 5 is a partially schematic front elevational view of the apparatusand method of FIG. 3.

FIG. 6 is another general schematic representation of a processaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

A system generally indicated by the reference numeral 1 for controllingodors in a public user space of a pit latrine is illustrated in FIGS.1-5. The system includes a pit latrine, generally 5, an incineration oroxidation unit, generally 7, a latrine gas supply conduit 9 equippedwith a mechanical ventilation unit such as an in-line fan 10 powered bya motor 10A, the conduit 9 connecting the latrine 5 with theincineration unit 7, and a conduit or stack 11 for removal ofsubstantially oxidized and deodorized gas from the incineration unit 7.A fuel storage unit 13 is connected to the incineration unit 7 by aconduit 15. Typically, the pit latrine 5 is already in existence andfresh air for the oxidation process enters through a housing 17 thatdefines an enclosed user space 18 of the latrine 5. Specifically, theair enters into the space 18 through one or more existing vents 19located on the housing 17. In the illustrated embodiment, a controlsystem 20 communicates with the unit 7 and the fan motor 10A and ispowered by a battery system 21 that is recharged by a solar panel 22.The control system 20 may be utilized to cycle the fan 10 andincineration unit 7 on a time dependent schedule to optimize fuel usage.

As indicated above, the system 1 according to the invention may be usedwith an existing pit latrine or incorporated into a new pit latrinesystem. It is foreseen that a system and process according to theinvention may also be utilized with a portable toilet. Additionally, itis foreseen that such a system and process according to the inventionmay be used to deodorize enclosed spaces for holding animals, such aspig operations.

A pit latrine 5 typically includes a pre-manufactured concrete structure23 forming a vault or waste reservoir chamber 25, the structure beinginstalled into the ground. The housing 17 that provides the enclosedpublic use space 18 is then built over the vaulted structure 23. One ormore toilets 27 located in the space 18 empty directly into the vault25. A portion 30 of the structure 23 is typically outside the housing 17and includes a “pump-out” opening 33 communicating with the vault 25that is typically covered by a man-hole cover 35. The pump-out opening33 is modified (as shown in FIG. 2) or a second opening 37 (as shown inFIG. 4) is formed for direct gas-flow communication with the vault 25.The opening 37 includes a cover 39 attached to the latrine gas conduit 9resulting in the conduit 9 being directly flow connected to the vault 25and the oxidation unit 7. With reference to FIG. 2, alternatively, thelatrine gas conduit 9 may be connected via a conduit 40 (shown in dottedlines) to a new or existing vault vent stack 41.

Gas from a pit latrine typically has a composition identified in Table Ibelow. Thus, such gas is rich in oxygen, with the odorous compounds orcomponents being present in relatively small amounts. According to anaspect of the invention, the noxious compounds present in the airlocated in the latrine are oxidized using a catalytic incinerator withair being supplied for the oxidation process. It is noted that it hasbeen found that complete oxidation of the noxious compounds is notrequired for adequate odor removal. For example, in an embodimentaccording to the invention wherein the fan 10 is included, the fan aidsin removing air from the public user space. Then, the noxious compoundsfound in the air are either fully or partially oxidized in the catalyticincinerator. Any remaining noxious compounds rise high above the unit 7due to the higher temperature of the flue gas as compared to thesurrounding air, and are dispersed without causing odor problems innearby areas. Catalytic incinerators operate very similar to thermalincinerators, with the primary difference that the gas to be oxidizedpasses through a catalyst bed rather than the flames of a thermalheater. The catalyst has the effect of increasing the oxidation reactionrate, enabling conversion at lower reaction temperatures than in thermalincinerator units. Thus, the oxidation is performed at a safertemperature and the catalytic combustion of the fuel typically is moreefficient than when burned using a flame.

TABLE I PIT GAS - COMPOSITION (MOLE %) N₂ 80.6595 O₂ 19.0 C₁ (HC's)(ND-3000 ppm) 0.30 CO₂ (400 ppm) 0.04 NH₃ (4 ppm) 0.0004 H₂S (ND-0.5ppm) 0.00005 RSH (ND-0.1 ppm) 0.00001 SO₂ (ND-0.1 ppm) 0.00001 Benzene(ND-0.5 ppm) 0.00005 Total 100.00

With particular reference to FIGS. 2-5, according to the invention, apreferred incineration/oxidation unit 7 according to the invention fordeodorizing a public use space of a pit latrine is a catalytic heater45, available, for example, from Bruest Catalytic Heaters, Independence,Kans. The catalytic heater 45 is a conventional gas catalytic heaterknown in the art that includes a fuel supply inlet and a catalyst bedthat utilizes a platinum or other transition metal catalyst to generateheat from a flame-less catalytic reaction, between, for example propaneand oxygen. Such heaters are typically used for space heating andindustrial instrument heating. The catalytic heater 45 is commerciallydesigned to utilize a readily available fuel gas, such as propane,ethanol or natural gas, to produce heat and thus to provide an efficientalternative heating source wherever flame-less heat is desired. Withouta flame, the fuel gas is oxidized (catalytic combustion), in thepresence of oxygen, to form carbon dioxide, water vapor and heat.According to the invention, the catalytic heater 45 is utilized to heatand oxidize noxious gas from a latrine wherein the oxygen source for thereaction performed in the catalytic heater 45 is air drawn through thevents 19 of the housing 17, into and through the toilet 27 or toilets,through the latrine vault 25, and out of the vault opening (33 or 37 orstack 41). Such oxygen source also advantageously includes the odorouscomponents or compounds listed in Table I above that are present withinthe public use space 18, the toilets 27 and the vault 25. In theillustrated embodiment, the fuel is propane drawn from the fuel tank 13through the conduit 15 into the catalytic heater 45. During theoxidation process of the propane, odorous components in the air streamfrom the latrine vault are converted into less odorous or non-odorouscompounds via oxidation.

Sufficient heat evolves from such process to raise the temperature ofthe catalytic bed of the heater, and thus oxidation continues as long asa fuel gas (such as propane) and oxygen from the latrine gas(air+odorous components) are supplied. Therefore, it is possible toinitialize the oxidation process by heating the catalyst bed using, forexample, an electric resistance heating element. Thereafter, theresistance heater is not needed. It is also foreseen that the hot gasexiting the catalytic heater may be used to preheat gas entering theheater, if desired. Furthermore, with reference to FIG. 1,alternatively, a hot gas stream 47 exiting the catalytic heater may beused directly or indirectly (e.g. heat exchanger) to heat the public usespace 18 of the pit latrine 5 during cold winter months.

In the illustrated embodiment, the fan 10 is disposed in the line 9located between the vault 25 of the pit latrine 5 and the catalyticheater 45 and draws air out of the vault 5 and into the heater 45. Thus,the fan provides advantageous positive air flow through the enclosedpublic user space 18 and through the toilet 27 or toilets, directingfecal odor away from people using the toilet 27. The fan 10 further aidsin propelling a deodorized air stream through the heater 45 and out thestack 11. The fan 10 can be operated with or without the heater 45 beingin operation, providing some relief from fecal odors in the enclosedpublic use space 18 even when the heater 45 is not in operation. Theillustrated fan 10 is powered by batteries 21 that are charged by solarpower 22 or alternatively, an electrical connection. When the heater 45is operating, the heated off gasses flowing out of the catalytic heater45 will rise to a sufficient elevation to allow for dispersion of anyun-reacted noxious compounds at a distance from the latrine andsurrounding public use area.

In other embodiments according to the invention, one large catalyticheater 45 or two or more smaller catalytic heaters 45 are utilizedwithout using the fan 10 to draw the air and odorous components from thelatrine vault 25. In such embodiments, as long as propane is fed intothe catalytic heater 45, the oxidation of the propane in the heater 45draws air (oxygen) from the vault 25 through the line 9 and into theheater 45. Thus, air is advantageously positively drawn into and throughthe toilets 27, drawing fresh air into the enclosed public use space 18defined by the housing 17 and keeping fecal and other odors away fromthe users of the toilets 27 located within the enclosed space 18.Furthermore, the out-gas conduit or vent stack 11 may be designed to aidin drawing a natural draft to draw the latrine gas out of the pitlatrine. It is believed that the stack 11 may also create a slightvacuum in the vault 25 that causes air from outside the vault to bedrawn into the latrine building through the vents 19 and into the vault25 through the toilet or toilets 27.

In the illustrated embodiment, fuel for the heater 45 is preferablypropane stored in the receptacle 13 that is typically a household orindustrial sized storage tank with the size being determined by howoften the storage tank is to be re-supplied. Other fuels, such asnatural gas, ethanol, butane, hydrogen and methanol may also be used inprocesses of the invention.

As illustrated in FIG. 2, apparatus according to the inventionpreferably include certain safety features, such as a check valve 50 toprevent back flow of fuel (e.g. propane) into the vault 25 and isolationvalves and regulators, generally 52, typically supplied by the catalyticheater vendor. Other details of the illustrated system include an excessflow valve 54 downstream of the fuel storage tank 13 and a coupling 55near the vault structure 23, allowing for the removal of the man-holecover 35.

With reference to FIGS. 3-5, other features of the illustrated apparatusaccording to the invention include a rain cap 60 disposed near a top 62of the vent stack 11. The vent stack 11 is insulated and extends abovethe roof eave 66. The fuel supply line 15 is preferably buried. Theheater 45 is preferably mounted on a stand 68 so as to be spaced fromthe top of the concrete pit latrine structure 30. The illustrated heater45 may be protected by a two-part (clam-shell) cabinet 72 that may belocked. In other embodiments according the invention, the heater 45 ismounted on the roof of the housing 17 or the stand 68 is elongate, sothat the heater 45 is mounted at an elevation at or above the roof line66. Such mounting improves the security of the system by reducing thelikelihood of tampering.

Table II sets forth additional details of the heater 45, fuel storage 13and conditions of operation for the illustrated embodiment according tothe invention:

TABLE II SAMPLE APPARATUS/OPERATING CONDITIONS Incinerator Type:Catalytic Pre-Heat: Internal (325-350° F.)Only for start-up Heat Flux:6000 Btu/ft² design/3000 Btu/ft² turndown Turndown: 2:1 Duty: TBD -Dependent on latrine size/application NORM Temp: about 400° F. (withfan) Max Temp: about 850° F. Excess O_(2:) TBD by calculations FuelType: HD-5 Propane (94% C3, 5% C2, 1% i-C4) Storage: 250 gals/500 galsdepending upon difficulty of re-filling Provided by local propanesupplier Controls: Regulator and other necessary controls provided bysupplier Pressure: 100-250 psig - dependent upon ambient (supply)temperature Pressure: 11 in H2O as regulated at the heater (heater)Local Conditions Temperature: −20 to 110° F. Elevation: 0 to 4500 ftabove MSL Heater de-rated 4% per 1000 ft above 4500′ Humidity: 0 to 100%Fan Volume: TBD for each application Power: DC Controls PLC controls forscheduling of heater/fan cycles Power: 110 VAC or solar panel

With reference to FIG. 6, as previously mentioned, process and apparatusaccording to the invention may be utilized to remove fecal and otherhuman body or animal odors from a substantially enclosed space otherthan pit latrines. For example, a catalytic heater 78 or series ofheaters identical or similar to the heater 45 previously describedherein may be directly flow connected to a variety of waste reservoirsor containment members. For example, a small catalytic heater may bedirectly flow connected to a waste pail or lower waste container of aportable toilet. Or, on the large end, one or more heaters 78 may beflow connected to a waste reservoir 80 or pit located beneath oradjacent to a substantially enclosed space 84 of a pig or other confinedanimal feeding operation. The process illustrated in FIG. 6 is otherwisethe same as described above with respect to the pit toilet system 1.Fresh air 82 is drawn into and through the enclosed area 84 and acrossor through the pit or waste reservoir 80 and into the heater 78. Aventilation system, such as an in-line fan 86 similar to the fan 10previously described herein may be located in a conduit 88 flowconnecting the gasses from the waste reservoir 80 to the catalyticheater 78. The system includes a conduit or stack 90 for removal ofsubstantially oxidized and deodorized gas from the unit 78. A fuelstorage unit 92 for propane or other types of fuel previously describedherein is connected to the unit 78 by a conduit 94. As with the system1, heated off-gasses flowing through a line 98 may be directed toward orotherwise used to heat the enclosure 84.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

1. A method of controlling odor within a user space of a pit latrine, the latrine having a vault flow connected to at least one toilet, the method comprising the steps of: a) directly flow-connecting the vault to an oxidizer; b) drawing air from the user space through the at least one toilet, through the vault and into the oxidizer; and c) performing an oxidation reaction in the oxidizer, the oxidation reaction using oxygen for the reaction from the air and other gasses in the latrine vault, the oxidation reaction substantially destroying odorous compounds drawn through and from the latrine vault.
 2. The method of claim 1 wherein the oxidizer is a catalytic heater.
 3. The method of claim 2 including the step of flowing a fuel to the catalytic heater.
 4. The method of claim 3 wherein the fuel is propane.
 5. The method of claim 1 wherein gasses are drawn from the vault and into the oxidizer using a ventilation unit.
 6. The method of claim 5 wherein the ventilation unit is an in-line fan flow connected to both the vault and the oxidizer.
 7. The method of claim 5 wherein the ventilation unit is powered by a solar power charged battery.
 8. The method of claim 1 wherein the gasses are drawn from the vault into the oxidizer by the oxidation reaction being performed in the oxidizer.
 9. The method of claim 1 including the step of exhausting hot gas from the oxidizer up a conduit, the heated gasses rising in a thermal plume, dispersing any odors remaining after the oxidation process.
 10. The method of claim 1 including the step of flowing hot exhaust gas from the oxidizer to the housing to heat the user space.
 11. A method of controlling human or other animal fecal odor within a substantially enclosed space, the space having a containment member for collecting fecal matter, the method comprising the steps of: a) directly flow-connecting the containment member to a catalytic heater; b) drawing air from the substantially enclosed space through the containment member and into the heater; and c) performing an oxidation reaction in the heater, the oxidation reaction using oxygen for the reaction from the air and other gasses drawn through and from the containment member, the oxidation reaction substantially destroying odorous compounds drawn through and from the containment member.
 12. The method of claim 11 wherein gasses are drawn from the containment member and into the oxidizer using an in-line fan flow connected to both the containment member and the oxidizer.
 13. In a pit latrine having a structure forming a vault connected to one or more toilets, the improvement comprising: a) a flameless heater that performs an oxidation reaction; and b) a conduit flow connecting the vault with the heater.
 14. The improvement of claim 4 wherein the heater is a catalytic heater.
 15. The improvement of claim 13 further comprising a mechanical ventilation unit flow connected to the conduit.
 16. The improvement of claim 15 wherein the mechanical ventilation unit is an in-line fan.
 17. The improvement of claim 15 further comprising a control system for cycling the ventilation unit and the heater operations on a time dependent schedule to optimize fuel usage. 